The Impact of Radiation on the GABLS3 Large-Eddy Simulation

The impact of including radiative transfer in simulations of the large-eddy case of GABLS3 is assessed. A simple radiation scheme, specifically designed for use in this case, is described. The scheme is used in two of the large-eddy models
participating in GABLS3. Infra-red radiative processes cause a modest deepening of the developed stable boundary layer, but cumulative radiative cooling of the residual layer through the simulation reduces the stability of the inversion capping the mixed layer that develops after the morning transition. The mixed layer therefore grows
considerably more rapidly than in the standard case from which radiation is omitted, resulting in better agreement with the observed profiles of potential temperature. Solar radiative heating of the atmosphere has a smaller impact on the development of the mixed layer than infra-red radiative cooling and slightly reduces the rate of growth of the mixed layer compared to simulations including infra-red radiation alone.